1. Technical Field
The present invention relates to an image processing technology to generate output data used when an image displayed on a display device is to be output by an output device.
2. Description of the Related Art
In general, in order to match colors between devices such as a monitor and a printer, a color matching process is used. Where color matching is carried out in order to print on a printer an image displayed on a monitor, for example, first, the image data expressed in a color space used for monitor display is converted, using a monitor device profile, into image data expressed in a device-independent color space (e. g., the L*a*b* color space). The post-conversion image data is further converted, using a printer device profile, into printer output image data expressed in a color space used for printer output. By printing the image using the printer output image data generated in this fashion, the color of the printed image can be matched to the color of the image displayed on the monitor.
Here, a device profile describes information pertaining to the color reproduction of a device. A device profile includes an association table that associates color data in a color space that depends on a device (a device-dependent color space), such as a color space used for the monitor display or printer output described above, with color data in a color space that does not depend on a device (a device-independent color space), such as the L*a*b* color space described above. A device-independent color space is also called a PCS (Profile Connection Space).
Where color matching is to be performed for printing onto a printer an image displayed on a monitor, two color space conversion processes are executed: (1) color space conversion to convert color data in the device-dependent color space used by the monitor into color data in a device-independent color space, and (2) color space conversion to convert the color data in the device-independent color space into color data in the device-dependent color space used by the printer.
These two color space conversion processes are executed after a print execution instruction is input. In other words, when a print execution instruction is input, the monitor display image data is converted into image data expressed in a device-independent color space, this converted image data is then converted into printer output image data, and finally printing is carried out using the generated printer output image data.
A technology is described in U.S. Pat. No. 5,423,906 in which, in order to shorten the print processing time from the time of input of the print execution instruction, a profile is created by combining the monitor device profile and the printer device profile, and the monitor display image data is converted directly into the printer output image data using this combined profile without using device-independent color space color data. In general, the time required for combining two device profiles is usually shorter than the time required for a single image data color space conversion operation. Consequently, in this technology, the processing time after input of a print execution instruction is shorter than in the case where two separate color space conversion operations are carried out.
However, in the above technology, because combining the two device profiles results in the loss of a certain amount of device profile information, there may be a deterioration in the accuracy of color matching. Furthermore, in the above technology, because the processes of combining the two device profiles and carrying out color space conversion based on the combined profile are carried out after input of a print execution instruction, there is room to further reduce the processing time associated with output following input of the print execution instruction.
This problem does not arise only where color matching is performed between a monitor and a printer, and may occur when color matching is performed between any two devices that include an output device.